#define _CRT_SECURE_NO_WARNINGS 1
bool _isSymmetric(struct TreeNode* root1, struct TreeNode* root2)
{
    if (root1 == NULL && root2 == NULL)
        return true;

    if (root1 == NULL || root2 == NULL)
        return false;

    if (root1->val != root2->val)
        return false;

    return _isSymmetric(root1->left, root2->right) && _isSymmetric(root1->right, root2->left);
}
bool isSymmetric(struct TreeNode* root)
{
    return !root || _isSymmetric(root->left, root->right);
}
